Radioactivity
Advances in a Theory That Has Enabled Us to Study Natural Transmutation
Features
Liquid Trade Wastes
A Difficult Problem in River Polution
Collections of the New York Aquarium
A Famous Institution Known to Naturalists and Sportsmen Throughout the World
Catalytic Agents
Their Relation to Modern Methods
Red Color of Faint Stars
The Nature of Ball Lightning
A Curious Phenomenon, and Attempts to Explain Its Nature and Action
Ammonia a Heat Vehicle
A Popular Explanation of the Refrigerating Process
Reproducing Prehistoric Monuments
Valuable and Clever Archæological Work at Quirigua, Guatemala
Good Water for Homes
Future Methods of Utilizing Coal
Economic Problems That Are Beginning to Attract Attention
Formulas for Glass Manufacture
Railway Exhibits at the Panama-Pacific Exposition
Details and Construction of the Steam and Electric Locomotives
Recent Progress in Astrophysics—II
Many Important Discoveries That Add to Our Knowledge of the Heavenly Bodies